There are driving situations where an anti-lock brake system (ABS) is activated for very short periods, such as hitting a patch of ice or a bump while braking. For such events, the ABS signal can be “ON” for as little as 140 milliseconds. Events such as these may be classified as “improper” ABS activation because of their transient nature. In some regenerative braking control strategies, the regenerative braking torque is set to zero as long as the ABS is “ON”; this includes the transient ABS events described above. This elimination of regenerative braking torque is undesirable in that it reduces the amount of regenerative braking energy that the vehicle can capture, and it is unnecessary for these very transient ABS events. In addition, such a control strategy may include a delay between when the ABS event has ended and when the regenerative braking torque is allowed to be non-zero; this further reduces the potential for capturing regenerative braking energy.
Other control strategies may react to an ABS event by adjusting a target regenerative braking torque so that regenerative braking is controlled to try to exactly meet the target value. This is also inefficient, in that the target value may not represent an optimum amount of regenerative braking that could be captured. Stated another way, forcing the regenerative braking torque to meet a certain target value without destabilizing the vehicle would require constant adjustment of the target value in order to ensure that regenerative braking was being performed at optimum levels. Therefore, a need exists for a vehicle and method for controlling regenerative braking that is able to account for transient ABS events and does control the regenerative braking so that it is forced to meet a target regenerative braking torque.